100330-lecture13 - EE522 Communications Theory Spring 2010 Instructor Hwang Soo Lee Lecture#13 Noncoherent Demodulation 1 Announcements Homework#5

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1 EE522 Communications Theory Spring 2010 Instructor: Hwang Soo Lee Lecture #13 – Noncoherent Demodulation
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2 Announcements ± Homework #5 Distributed ² Due Tuesday, March 30 ± Handouts: ² Lecture Notes #13
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3 Noncoherent Receivers ± Up to this point, we have assumed that all receivers are coherent (i.e. they are able to detect and track the phase of the signal). ² For telephone lines, fixed microwave links, and some fixed satellite links, coherent reception is frequently possible. ± While there are practical circuits (phase lock loops) which accomplish this, in many cases strict phase synchronization is not possible. ² For many mobile and wireless systems, multipath components and movement of the receiver prevent phase synchronization.
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4 Types of Noncoherent Reception ± PSK and QAM signals represent information with the phase of the signal. ± In many cases, even though it is not possible to detect the absolute phase of a signal, it is possible to detect the difference in phase from one symbol to the next. ± For FSK with sufficiently spaced tones, demodulation can be accomplished with no phase information using a noncoherent receiver.
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5 Differential Encoding of Data ± Consider BPSK modulation: ± Differential Encoding Transforms Raw Data: ± Rule: “Change the phase if input data is a 1”
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6 Example of Differential Encoding
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This note was uploaded on 11/23/2010 for the course EE EE522 taught by Professor Eeehwangsoo during the Spring '10 term at Korea Advanced Institute of Science and Technology.

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100330-lecture13 - EE522 Communications Theory Spring 2010 Instructor Hwang Soo Lee Lecture#13 Noncoherent Demodulation 1 Announcements Homework#5

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